CN114341553A - Method for controlling a device consisting of a heat pump and a three-way mixer valve - Google Patents

Abstract

The present invention relates to a method for controlling an installation comprising a heat pump for circulating a heating medium in a closed heating circuit and a three-way mixer valve, the three-way mixer valve having The first inlet is connected to the boiler, the second inlet of the three-way mixer valve is connected to the return line of the load circuit, and the outlet of the three-way mixer valve is connected to the inlet line of the load circuit, wherein the supply The heat pump knows the temperature of the delivery flow through the pump, characterized in that the control means actuates the mixer valve with at least two different switching positions, and takes into account the corresponding switching positions and the corresponding switching positions. The temperature of the medium at at least one of the valve connections which is not connected to the heat pump is calculated with the delivery flow temperature determined by the pump.

Description

Method for controlling a device consisting of a heat pump and a three-way mixer valve

technical field

The invention relates to a method for controlling a device comprising a heat pump for circulating a heating medium in a closed heating circuit and a three-way mixer valve, the three-way mixer The first inlet of the valve is connected to the boiler, the second inlet of the three-way mixer valve is connected to the return line of the load circuit and the outlet of the three-way mixer valve is connected to the inlet line of the load circuit.

Background technique

The mixers used in the heating circuit are three-way valves and are used in particular for regulating the inlet temperature in a closed heating circuit. This treatment is often chosen if a common heat source (boiler or remote heating system) is supposed to supply several separate heating circuits at the same time. A specific application is the supply of different buildings or indoor areas from a common heat source. In this case, the boiler control mechanism cannot individually adjust the inlet temperature of the connected load circuit. To remedy this, three-way valves are used in each load circuit, the inflows of which are connected to the boiler and the return line of the load circuit. The valve outlet is connected to the inlet line of the load circuit.

A schematic diagram of a heating circuit with mixers can be seen from FIG. 1 . The heating device 1 is connected to the first inflow port of the mixer 2 . The second inflow is connected to the return line 7 of the heating circuit. The mixer 2 is connected on the outlet side to a circulating pump 4, which is installed in the inflow line 6 of the heating circuit and feeds the heating medium back through the connected load circuit 3 and the return line 7 to the heating circuit. Boiler 1. The control mechanism of the boiler 1 knows the outside temperature and defines the target value of the medium temperature accordingly. The mixer valve 2 has its own regulating mechanism with integrated temperature sensor 5 in order to be able to regulate the inflow temperature to the specified target value in this way. Therefore, the inflow temperature is measured by means of the temperature sensor 5 and adjusted to a target value. If the detected actual temperature deviates from the target value, the mixer 2 adjusts its valve position for changing the mixing ratio between the heated medium of the boiler 1 and the heating medium returned from the return line 7 .

SUMMARY OF THE INVENTION

The task of the present application is to operate a heating circuit system with integrated mixer valves more efficiently on the one hand and to reduce the number of components required in order to achieve, in particular, a more compact structure.

This task is solved by a method according to the features of claim 1 . Advantageous configurations of the method are the subject of the dependent claims.

According to the invention, a method for sensorless acquisition of the temperature of the medium in one of the valve ports is proposed. The starting point of the method is that information about the current inlet temperature or, alternatively, the return temperature is already available within the system. This temperature value can be detected, for example, by a temperature sensor, or else it can be provided by an installed heat pump, which is able to measure or estimate the temperature of its delivery flow. The method now provides that the mixer valve is actuated with at least two different switching positions. These switching positions are distinguished by the different mixing ratios of the two inflow openings. By evaluating the available temperature values, either for the supply line or not for the return line, it is now possible to calculate the temperature values at the mixer valve, taking into account the switching position-dependent mixing ratio of the mixer valve The temperature of the medium at at least one of the valve ports. That is, if there is already information about the inflow temperature, the return temperature and/or the temperature of the medium from the heating boiler can be calculated by means of the method. If the return temperature is known instead, the inflow temperature and/or the temperature of the medium from the boiler can be calculated.

By means of the method, additional operating parameters can be determined, which enable further applications as will be explained below, without the need for additional sensors for this purpose.

It is particularly advantageous if the mixer valve is actuated by means of a control device which is also responsible for the regulation of the heat pump. In this way, a separate additional control of the mixer valve can be dispensed with, which enables a further saving of possible components. For example, it is conceivable that the integrated pump control of the heat pump takes over the actuation of the mixer valve, that is to say, in particular by means of the mixer valve, the regulation of the inflow temperature and carries out the method according to the invention. Here, the required temperature information is preferably provided directly by the heat pump.

As already briefly mentioned above, it is conceivable that the control device knows the temperature of the medium there, for example by means of a heat pump installed in the inflow line, which heat pump either by means of a sensor device or sensorless by means of a suitable The estimating algorithm obtains the corresponding temperature autonomously. On the basis of this known medium temperature in the inflow line, the medium temperature in the return line can be calculated by means of the method according to the invention, without the need for a separate sensor device for this purpose .

A possible solution for calculating the desired medium temperature is based on the arrangement that, for each switching position, a mathematical equation is determined, which mathematical equation includes, as equation parameter, the mixing ratio for the current switching position, namely two The mixing ratio of the inflow to the outflow and the at least three temperature values for each valve connection. If the mixer valve is now operated in at least two different switching positions, the desired unknown temperature can be solved by means of the equivalent method of the at least two equations. For the execution of the method, it is necessary to activate at least two different switching positions of the mixer valve, ideally one after the other at short time intervals, in order to enable the load circuit or in the boiler regulation The possibility of change is minimized. The calculation is more robust if more than two switching positions are activated, since the accuracy of the calculation results can be improved in this way by equivalence of multiple equations.

For example, it can be considered that the following equations can be established for each switching position:

where Tv is the inflow temperature, _TR is the return temperature, TK is the temperature of the heating medium provided by the boiler and _S is the spool position of the mixer valve. In this case, the parameter S can have a value from 0 to 1, wherein S=0 represents a switching position of the three-way valve in which only medium is fed from the boiler into the inflow line, while in the When S=1, only the medium is fed from the return port of the three-way valve into the inflow line.

As already briefly described, the information now available on the feed and return temperatures allows for different application options. On the one hand, a calorimeter can be implemented with the aid of the currently available value pairs consisting of the inlet and outlet temperatures, which provide the plant operator with an indication of the consumed heating power of the building to be heated. The heat is calculated according to the following equation:

To implement a calorimeter, the delivery flow Q, the return temperature _TR and the feed temperature Tv must be known. The delivery flow and temperature of the delivery medium and, depending on the installation position of the pump, the inflow or return temperature are inherently present for the pump control. With the aid of the method according to the invention, unknown temperatures can be calculated and thus a calorimeter can be realized.

It is particularly advantageous to operate the mixer and the pump as a multi-variable system with the aid of the method and to carry out an optimized, coordinated regulation of the inflow temperature and the head/delivery flow accordingly.

For example, the heating power consumed by a building requiring heating is combined as follows:

，

,

where P _H represents the power output at the heating body of the load circuit, c _P represents the heat capacity of the water, Q corresponds to the delivery flow of the pump, ρ is the density of the water, and T _V , _TR are the inflow piping Or the corresponding temperature in the return line. All the aforementioned parameters are known to the control mechanism so that the power output in the load circuit can be calculated at any time.

Now, it is advantageously proposed that, by means of a targeted reduction in the pump speed and the inflow temperature, by means of a corresponding actuation of the mixer valve, it is checked whether, even with a reduction in the rotational speed or in the inflow temperature, sufficient supply the room to be heated. Therefore, the power output is calculated again for each operating state, that is to say with a reduction in the rotational speed and/or a reduction in the inflow temperature, according to the above-mentioned formula. If the power output continues to remain constant, it can be considered that the room to be heated is adequately heated. The reason for the constant power output is that the thermostatic valve is adjusted according to the demand at the heating body of the room to be heated and responds appropriately when the rotational speed is reduced or the inlet temperature is lowered accordingly, so that the consumption is finally reduced. The heating power remains almost constant. The heating power is actually reduced only in the event of an undersupply.

Therefore, for the method according to the invention, it is advisable to reduce the rotational speed of the pump and/or the inflow temperature until a corresponding reduction in the heating power and thus a lack of supply is detected. If this is the case, the inflow temperature and/or the pump rotational speed are then increased by the control device just enough to still ensure an adequate supply to the building to be heated. By means of this treatment, the rotational speed and the inflow temperature can be adapted as precisely as possible to the required heat of the building, so that a more efficient operation of the entire plant can thus be ensured. This is because an excessively high inlet temperature leads to unnecessary heat loss in the piping system, while a set rotational speed that is too high means an excessive flow consumption of the heat pump.

According to an alternative configuration of the method, provision can be made to adjust the inflow temperature and the pump speed according to definable weightings after detection of an undersupply, in order to take into account the two different priorities. parameter. The reduction of the inflow temperature preferably has a higher priority than the reduction of the rotational speed, that is to say, for an operating mode in which the room to be heated is supplied just enough, an attempt is made to reduce the inflow temperature as much as possible, Conversely, a higher rotational speed of the heat pump is tolerated for this. The reason for this treatment is that (with regard to the overall balance) the losses due to excessively high medium temperature are given more weight than the electrical losses of the pump due to excessively high rotational speeds.

Another aspect of the invention relates to a method for operating a heating installation consisting of separate load circuits and a common heat source, as already described in the introduction. According to the invention, it is proposed here that each load circuit uses at least one device for carrying out the aforementioned method, which device consists of a circulation pump and a mixer valve. The control of the respective device or mixer valve can be carried out by means of a central control mechanism for all or at least a part of said device or mixer valve. It is also conceivable that a separate control unit is provided for each device. It is likewise conceivable that the central control or separate control assemblies can also carry out the control of the respective circulation pumps.

In addition to the method according to the invention, the invention also relates to a device comprising a heat pump for circulating a heating medium in a closed heating circuit, and three heat pumps with a total of two inflow openings and one outflow opening. through the mixer valve. Furthermore, the claimed device comprises a common control mechanism for regulating the heat pump and for controlling the mixer valve, in order thereby to adjust the inflow temperature to the desired temperature. The use of a common control mechanism for mixer valve and pump regulation enables a system with fewer components and thus also a more compact structure.

Advantageously, the common control unit for the mixer valve and the heat pump is configured to carry out the method according to the invention, whereby the return temperature is preferably determined. Correspondingly, the same advantages and properties as those already explained above with the aid of the method according to the invention apply to the device.

In addition to the device, the invention also relates to a heat pump with an integrated control, wherein the control is configured to control not only the rotational speed of the pump for regulating the pump head but also the inflow temperature Switching position of the three-way mixer valve. The integrated control of the heat pump is ideally configured to carry out the method according to the invention.

Finally, the invention also covers a heating installation consisting of separate load circuits and a common heat source. According to the invention, it is proposed here that each load circuit uses at least one device according to the invention for carrying out the method according to the invention. With the aid of a central control, all mixer valves and/or circulation pumps can preferably be actuated centrally according to the method according to the invention. However, each load circuit can equally well be equipped with its own control assembly for controlling the corresponding mixer valve or the corresponding circulating pump.

Description of drawings

Further advantages and properties of the invention will be explained in more detail below with the aid of the exemplary embodiments shown in the drawings. in:

Figure 1 shows a schematic diagram of a heating circuit with a mixer,

Figure 2 shows a detail view of a three-way mixer valve with corresponding inflow and outflow ports.

Detailed ways

In contrast to conventional mixer valves, it is proposed for the embodiments of the invention explained below that the adjustment of the mixer valve is transmitted to the pump, ie to the pump control. There are two main advantages from this:

1. Since the temperature of the delivery flow is generally known for the heat pump, the additional temperature sensor 5 can be dispensed with (see FIG. 1 ). Furthermore, a separate control unit of the mixer 2 can also be dispensed with.

2. If the heat pump is responsible for the control of the mixer, the heat pump can simultaneously acquire the inflow and return temperature by appropriate manipulation of the mixer 2 . The algorithms used to determine the inlet and return temperatures are described below.

Determination of inflow and return temperature

Figure 2 schematically shows the inflow and outflow ports of the three-way valve. The spool position S of the three-way valve can have a value between zero and one. In the spool position S=0, only medium is fed from the boiler into the inflow line. In the case of S=1, only the medium is fed from the return line into the inflow line. For all other spool positions, the delivery flow is divided according to Equation 3.

（方程式1）

(Equation 1)

（方程式2）

(Equation 2)

（方程式3）

(Equation 3)

Equation 3 consists of the known parameter S (regulated by the pump) and the temperature TV in the _inflow line (detected by the pump, as long as the pump is installed in the inflow line). Two unknown parameters _TR and _TK remain. The pump is now able to change the spool position S for a short time. If the pump has been set with two spool positions, two pairs of values for _TR and _TK are generated and all unknown temperatures can be determined by means of Equation 3. The calculation is more robust if more than two spool positions are activated. Since the pump in the regulated operation actually changes the valve slide position continuously, the inlet and return temperatures are also continuously detected. Only in the resting state the spool position does not change. However, in a static state, the inflow and return temperature will also be stable, so that there is sufficient information continuously.

Application of the pump with knowledge of the inlet and return temperatures

Knowledge of the inlet and return temperatures can now be utilized by the pump. On the one hand, a calorimeter can be implemented because all necessary parameters (feed flow Q, return temperature _TR and feed temperature _TV ) are present for calculating the heat.

On the other hand, the mixer and the pump can be operated as a multi-parameter system, and thus the scheme of heat input into the building can be designed more efficiently. This efficient operation is described below:

The heating power input into the building by the heating body is calculated according to the following equation (equation 4):

（方程式4）

(Equation 4)

where P _H corresponds to the power output on the heating body, c _P is the heat capacity of the water, Q is the delivery flow of the pump, and ρ is the density of the water. _TV represents the temperature of the medium from the three-way valve (inflow temperature) and _TR represents the temperature of the medium in the return line. It should be noted that the density of water depends on the temperature of the medium. This correlation can be adequately approximated by the mean between the feed temperature and the reflux temperature ( _{TV - TR )} /2.

The pump can now directly adjust the inflow temperature T _V via the mixer position S and vary the delivery flow Q via its rotational speed. As long as no undersupply occurs, the heating power _PH remains the same continuously, since the heating body is regulated according to demand.

If, for example, the pump increases the rotational speed and thus the delivery flow Q, either the thermostatic valve closes and the delivery flow Q remains almost constant, or the difference between the inlet and return temperatures (T _V −T _R ) does not decrease. For both cases, the heating power P _H therefore remains almost constant.

The same applies when the pump changes the inflow temperature T _V by actuating the mixer valve. Either the thermostatic valve of the heating body corrects the increased heat input by delivering the flow Q, or the return temperature is adapted to the changed inflow temperature, so that the difference (T _V −T _R ) decreases.

The heating power _PH is likewise reduced only if the pump has already been reduced either in speed or inflow temperature so that an underfeed occurs. In this way, it is possible to precisely determine the range from which the undersupply occurs. With this knowledge, the pump can now adjust the delivery flow Q and the inflow temperature _TV in such a way that the heating system operates approximately above undersupply. This state increases the energy efficiency of the entire heating circuit, since an excessively high delivery flow leads to an excessively high pump speed and thus increases the flow consumption of the pump. Excessive inflow temperatures lead to increased heat losses in the piping system.

Therefore, these two values should be adjusted as low as possible. Again, the correlation between the delivery flow Q and the inflow temperature T _V should be chosen such that a low inflow temperature T _V has priority over a low pump speed, since the heat losses in the pipes are energy-wise Worse than the flow consumption of the pump.

Claims (15)

1. Method for controlling a device comprising a heat supply pump for circulating a heat supply medium in a closed heat supply circuit and a three-way mixer valve, a first inlet of which is connected to a boiler, a second inlet of which is connected to a return line of a load circuit and an outlet of which is connected to a feed line of the load circuit, wherein the heat supply pump knows the temperature of a transport flow through which the pump flows,

the control device is characterized in that the control device actuates the mixer valve with at least two different switching positions and calculates the medium temperature at least one of the valve connections that is not connected to the heat supply pump, taking into account the respective switching position and the delivery flow rate temperature determined by the pump.

2. The method according to claim 1, characterized in that the temperature of the delivery flow through which the pump flows corresponds to the inflow temperature, and in that the control means calculate the temperature of the medium in the return line.

3. Method according to one of the preceding claims, characterized in that an equation is defined for each switching position, which equation has as parameters the mixing ratio for the current switching position and the temperature value at the valve interface, and in that at least one unknown temperature is calculated for the at least two switching positions by means of a peer-to-peer method of the defined equations by means of the respective solution equations.

4. Method according to any of the preceding claims, characterized in that the temperature of the delivery flow of the pump is detected by a sensor or obtained by an estimation algorithm of the heat supply pump.

5. Method according to any of the preceding claims, characterized in that a calorimeter is implemented in the control mechanism using the known temperature of the transport flow and the calculated inflow or return temperature.

6. Method according to any one of the preceding claims, characterized in that the control unit determines the heating power output to the load circuit on the basis of a known delivery flow rate of the heating pump and known or calculated inflow and return temperatures, and reduces the inflow temperature by adjusting the mixer valve and the delivery flow rate of the heating pump by adjusting the pump speed until an insufficient supply of the load circuit is detected.

7. Method according to claim 6, characterized in that the control means adjust the mixer valve and/or the rotational speed in such a way that there is an energetically favorable operation with a rotational speed which is as low as possible and a low inflow temperature, in which operation there is just no starvation.

8. Method according to claim 7, characterized in that, in the setting of an energetically favorable operation, the reduction of the inflow temperature has a higher priority than the reduction of the pump speed.

9. Method for operating a heating system, which comprises a plurality of separate load circuits and a common heat source, wherein at least one device for carrying out the method according to one of the preceding claims is used for each load circuit, wherein a central control device for controlling the device or an integrated mixer valve or no more distributed control devices assigned to the device for controlling the respective mixer valve are provided.

10. The device comprises a heating pump for circulating a heating medium in a closed heating circuit, a three-way mixer valve having a total of three connections, and a common control unit for regulating the rotational speed of the heating pump and for controlling the mixer valve for regulating the inflow temperature.

11. The apparatus of claim 10, wherein the control mechanism is configured to perform the method of any one of claims 1 to 8.

12. The apparatus of any one of claims 10 or 11, wherein the control mechanism is integrated into the heat supply pump.

13. A heat supply pump with an integrated control mechanism, which is configured for speed regulation of the pump and for regulating the inflow temperature by means of the actuation of the three-way mixer valve.

14. The heat supply pump of claim 13, wherein the control mechanism is configured to implement the method of any of claims 1-8.

15. Heating installation comprising a plurality of separate load circuits and a common heat source, characterized in that at least one device according to one of claims 10 to 12 is provided per load circuit for carrying out the method according to one of the preceding claims 1 to 9, wherein a central control means for controlling the respective mixer valve of the device or alternatively control means which are distributed and associated with the device are provided.

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